1. Field of the Invention
The present invention relates to a storage device for photographic material, especially photographic paper or film.
2. Background Information
Storage devices for photographic material are used for the buffering of band-shaped photographic material during manufacturing or processing, for example, during photographic paper development or film processing. They are also used for indicating the length of the buffered photographic material band and for the control, for example, of the photographic material transport speed, outside the storage in dependence of the buffered length of the band material. Such displays or controls are known, for example, as dancers or dancer controls.
Conventionally, so-called roller storage devices are used for this storage. In those roller storage devices, a photographic band material meanders around guide rollers and along a transparent path between an inlet and an outlet of the storage. By displacement of the guide rollers relative to one another, the transport path in the storage device is lengthened when the guide rollers move away from one another or shortened when they approach one another. Guide rollers are positioned, for example, in several planes, especially in two planes and the length of the transport path is changed by changing the spacing between the axis of the guide rollers in the different planes. Especially the transport speed of the photographic band material at the storage outlet can be reduced or completely stopped by lengthening the transport path within the storage.
The guide rollers of the lowermost plane normally carry out an up and down movement for change of the transport path length. The lower guide rollers are thereby positioned on a sled and are therefore connected with each other. The sled together with the lower guide rollers serves as a weight member which keeps the photographic material tensioned along its path in the storage by way of its weight, whereby the lower guide rollers upon shortening of the photographic band material are moved upwardly against the weight and by the pull of the photographic material.
If the end of a photographic band material reaches the storage and passes therethrough or if the photographic material band ruptures, a free fall of the lower guide rollers with the sled can occur. In order to avoid this, a guide for the sled must be provided which includes brakes which are activated in such a situation, but otherwise allow a free up and down movement of the sled and the lower guide rollers.
For the threading in of the photographic band material, the lower guide rollers during storage operation are positioned above the upper guide rollers during storage operation so that the photographic band material can run straight between these guide rollers during the threading in. Thus, in order to reach the starting position for the threading in, the sled with the lower guide rollers must be moved up. Lifting devices are provided herefor which operate, for example, with chains, belts or spindles.
A sled for a storage arrangement must therefore be able to assume three operating conditions, namely, first, moving up"(for the threading in), second, braking" (at band rupture or band end), and, third, freely moveable under inherent weight" (during storage operation).
In order that the sled or the lower guide rollers can assume the above-mentioned three different operating conditions, brakes and clutches are provided in the prior art together with costly electrical controls.